package com.hit.basmath.learn.binary_tree;

import com.hit.common.TreeNode;

import java.util.Arrays;
import java.util.Deque;
import java.util.LinkedList;

/**
 * 297. Serialize and Deserialize Binary Tree
 * <p>
 * Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or transmitted across a network connection link to be reconstructed later in the same or another computer environment.
 * <p>
 * Design an algorithm to serialize and deserialize a binary tree. There is no restriction on how your serialization/deserialization algorithm should work. You just need to ensure that a binary tree can be serialized to a string and this string can be deserialized to the original tree structure.
 * <p>
 * Example:
 * <p>
 * You may serialize the following tree:
 * <p>
 * 1
 * / \
 * 2   3
 * / \
 * 4   5
 * <p>
 * as "[1,2,3,null,null,4,5]"
 * <p>
 * Clarification: The above format is the same as how LeetCode serializes a binary tree. You do not necessarily need to follow this format, so please be creative and come up with different approaches yourself.
 * <p>
 * Note: Do not use class member/global/static variables to store states. Your serialize and deserialize algorithms should be stateless.
 */
public class _297 {
    class Codec {
        private static final String spliter = ",";
        private static final String NN = "X";

        // Encodes a tree to a single string.
        public String serialize(TreeNode root) {
            StringBuilder sb = new StringBuilder();
            buildString(root, sb);
            return sb.toString();
        }

        private void buildString(TreeNode node, StringBuilder sb) {
            if (node == null) {
                sb.append(NN).append(spliter);
            } else {
                sb.append(node.val).append(spliter);
                buildString(node.left, sb);
                buildString(node.right, sb);
            }
        }

        // Decodes your encoded data to tree.
        public TreeNode deserialize(String data) {
            Deque<String> nodes = new LinkedList<>();
            nodes.addAll(Arrays.asList(data.split(spliter)));
            return buildTree(nodes);
        }

        private TreeNode buildTree(Deque<String> nodes) {
            String val = nodes.remove();
            if (val.equals(NN)) return null;
            else {
                TreeNode node = new TreeNode(Integer.valueOf(val));
                node.left = buildTree(nodes);
                node.right = buildTree(nodes);
                return node;
            }
        }
    }
}
